I usually ride alone unless I run into friends on the mountain. I find you can learn a lot faster riding solo if you have a set trick/technique you're focused on learning on that day.
That said, I still like riding with friends from time to time.
It's nice to have a group vibe and it can help give you that push you need, especially in the park when you're all tackling the same obstacles together.
If I end up riding with housemates who aren't as experienced, I'll just use it as a chance to work on my switch technique.